REVIEW OF STRIP AND BLOCK ADJUSTMENT DURING 1964-1967 
7 
errors. A detailed description of these 
methods can be found in ref. [38] and [39]. 
Most of the authors use a method that be 
longs to the first group. Especially simple is 
the method of block adjustment given by 
Roelofs [47]. Here, an internal block adjust 
ment is performed in which scale, azimuth, 
and shifts of the sections are adjusted sep 
arately. Thompson [49] and Van der Weele 
[50] describe the use of base lines in this ad 
justment. Thompson’s paper is of additional 
interest because it exposes the often read fal 
lacy that some errors in strip triangulation 
are by their nature of the third degree in the 
^-coordinate. 
References [38] and [39] describe a method 
of the second group in which the coordinate 
connections between models are enforced by 
choosing the transformed coordinates of the 
connecting points (or, rather, corrections to 
their approximate values) as parameters. 
This reduces the number of parameters from 
seven to just over four per model. 
References [41], [42], [52], and [53], too, 
enforce the coordinate connection but they 
use the well-known double summation of the 
effect of transfer errors. Although this reduces 
the number of parameters to those of one 
model of a strip, it produces condition equa 
tions for each control point and for each 
tie point between strips in which corrections 
to the transfers of scale, azimuth, and tilts 
occur as corrections to quasi-observations. 
Jerie, in the latter two references, has re 
duced the complications which this causes in 
the formation of the normal equations by the 
use of smoothing procedures and fictitious 
points. 
Especially in the case of sparse ground con 
trol, a provision for the elimination of system 
atic errors in the strip triangulation should 
be included. In [38], [52], and [53] this is 
achieved by including second-degree terms in 
the transformation. If one wishes to avoid this 
contamination with the idea of polynomial 
adjustment, the procedure in ref. [39] can be 
followed. Here, the conditions that the trans 
fer errors should be equal to zero are replaced 
by the conditions that, at least in the case of 
equal model widths, the transfer errors at 
each two successive connections should be 
the same. 
Strip Triangulation 
1. STRIP FORMATION FROM INDEPENDENT 
MODELS 
At several centres, the triangulation of 
independent models is followed by strip 
formation and polynomial strip- and block- 
adjustment. Ref. [55] to [64] treat the strip 
formation for that purpose. 
The strip formation consists in connecting 
each model to the preceding one by means of 
a similarity transformation. In most cases, 
an exact coordinate connection is made at the 
common perspective centre. Very simple 
formulas for this purpose are given by Thom 
son [59], [60], and Schut [57]. 
Reference [62] gives the standard procedure 
for determining the model coordinates of the 
perspective centres from grid measurements 
made at two heights. Ref. [55] describes the 
computation of these coordinates by resec 
tion, using measurements made at one height. 
The latter computation requires pre-calibra 
tion of the projection cameras. 
Inghilleri and Gaietto [55] perform only 
an approximate relative orientation in the 
analog instrument. The adjustment of the 
relative orientation, based upon recorded 
parallaxes, is included in the strip formation. 
2. TRIPLETS IN STRIP TRIANGULATION 
References [65] to [68] describe two 
methods of analytical strip triangulation 
based upon the orientation of triplets. Ander 
son and McNair perform independent orien 
tations of the triplets. The triplets are joined 
into strips by making the orientation of the 
centre photograph of a triplet and the bx of 
its first model equal to those obtained for 
this photograph and for this base component 
in the preceding triplet. Keller and Tewinkel 
perform the triplet orientation while enforcing 
the orientation of its first photograph and 
the strip coordinates of the points whose 
images lie across the centre of this photo 
graph. 
Consequently, with both methods the man 
ner in which two successive triplets are con 
nected and as a result the strip deformation 
caused by errors and by deformation of the 
photographs depends upon the direction of 
triangulation. This can be avoided by follow 
ing McNair’s recommendation [66] to connect 
successive independent triplets by similarity 
transformations using all common points. 
It has been claimed that triplet triangula 
tion results in a stronger or more rigid strip 
than triangulation by independent relative 
orientation and scaling of successive models. 
However, Moellman [69], using C&GS pro 
grams, reports that after second- or third- 
degree polynomial strip adjustment there is 
no way to distinguish between the results of 
the two triangulations. McNair [66] has ob 
tained better results from his triplet triangu-